1:12 (Standard ADA)
1:10 (Steeper, for shorter ramps)
1:8 (Maximum for steeper slopes)
Required Ramp Length
Understanding Wheelchair Ramp Calculations
Calculating the correct length for a wheelchair ramp is crucial for accessibility and safety. The primary factor determining ramp length is the total rise (the vertical height that needs to be overcome) and the desired slope ratio.
The Slope Ratio Explained
The slope ratio is expressed as "X:Y", where:
X represents the number of vertical units (rise).
Y represents the number of horizontal units (run) required for that vertical unit.
For example, a 1:12 slope means that for every 1 inch of vertical rise, you need 12 inches of horizontal run. A gentler slope (higher second number) requires a longer ramp, while a steeper slope (lower second number) requires a shorter ramp but is more challenging for users to navigate.
Commonly Recommended Slope Ratios:
1:12: This is the standard recommended by the Americans with Disabilities Act (ADA) for new construction. It offers a good balance between usability and space requirements.
1:10: This is a steeper slope that may be used in situations where space is limited, but it is more difficult to ascend for individuals using manual wheelchairs.
1:8: This is the steepest slope generally permitted and should only be used for very short rises where no other option is feasible. It is extremely challenging for most users.
The Calculation Formula
The formula to calculate the required horizontal run of the ramp is straightforward:
Required Horizontal Run = Total Rise × Slope Ratio (Y value)
For instance, if your Total Rise is 30 inches and you are using a 1:12 slope:
This calculated horizontal run represents the total length of the ramp surface needed. In the example above, the ramp would need to be 360 inches long horizontally.
Important Considerations:
Landings: Ramps longer than 30 feet (360 inches) in horizontal run should include level landings at least every 30 feet for resting. Landings are also required at the top and bottom of the ramp and at any point where the ramp changes direction.
Width: The minimum clear width of a ramp is typically 36 inches.
Handrails: Ramps with a rise greater than 6 inches or a horizontal run greater than 72 inches are generally required to have handrails on both sides.
Surfaces: Ramp surfaces should be stable, firm, and slip-resistant.
Local Regulations: Always consult local building codes and accessibility standards, as they may have specific requirements that supersede general guidelines.
This calculator provides the essential horizontal run. Professional installation and consultation with accessibility experts are recommended to ensure compliance and optimal usability.
function calculateRampLength() {
var riseInput = document.getElementById("rise");
var slopeSelect = document.getElementById("slope");
var resultDiv = document.getElementById("result");
var resultValueDiv = document.getElementById("result-value");
var resultUnitPara = document.getElementById("result-unit");
var disclaimerPara = document.getElementById("disclaimer");
var rise = parseFloat(riseInput.value);
var slopeRatioValue = parseFloat(slopeSelect.value);
if (isNaN(rise) || rise <= 0) {
alert("Please enter a valid positive number for the Total Rise.");
return;
}
if (isNaN(slopeRatioValue) || slopeRatioValue 30) {
disclaimerText += "Note: Ramps over 30 feet in horizontal length typically require intermediate landings. ";
}
if (rise > 6 || requiredRun > 72) {
disclaimerText += "Note: Ramps with this rise or length usually require handrails on both sides. ";
}
disclaimerText += "Consult local building codes and ADA guidelines for specific requirements.";
disclaimerPara.innerText = disclaimerText;
resultDiv.style.display = "block";
}